Self-cleaning Evaporator driven by MVR, the way to go!
Self-cleaning heat exchangers have been applied for decades and have proven to solve cases where fouling of the tubes caused severe problems. For the past 2 years Klaren International is active in India together with Shachi Engineering to supply Multi-Effect Evaporator (MEE) plants to treat difficult effluent from manufacturers of dye-stuff. In these plants one of the effects is equipped with the self-cleaning configuration while the other effects are of the conventional forced circulation type.
The reason to equip only one of the effects with the self-cleaning configuration is purely economic. The self- cleaning technology will require additional CAPEX but will give a higher availability and productivity of the plant and avoid cleaning costs. So, selecting the effect most prone to fouling can already make a huge step to increase the time between cleanings but it means that the other effects still can show fouling. This is one of the important reasons why a concept using Mechanical Vapour Recompression (MVR) is very interesting because there will only be one effect. So, the question about which effect to equip with the self-cleaning technology becomes obsolete.
In an evaporator driven by an MVR (or MVC which are synonyms), the vapour coming from the evaporation is compressed by a compressor to a higher pressure and temperature. This higher temperature allows the vapour to be used at the shell side of the heat exchanger in the evaporator where it condenses. In other words, all the energy used to evaporate or the latent heat is recovered. In a MEE this by definition is only done partially. Of course, the MVR requires energy to drive the compressor but overall the use of primary energy is significantly less.
The white paper “Self-cleaning evaporator driven by MVR, the way to go!” discusses the MVR with the self- cleaning system from different perspectives, its energy consumption, the experiences with self-cleaning, the design of it and the operational aspect of applying a compressor.